|Publication number||US7061212 B2|
|Application number||US 10/913,622|
|Publication date||Jun 13, 2006|
|Filing date||Aug 6, 2004|
|Priority date||Aug 8, 2003|
|Also published as||US20050030772, WO2005015718A2, WO2005015718A3|
|Publication number||10913622, 913622, US 7061212 B2, US 7061212B2, US-B2-7061212, US7061212 B2, US7061212B2|
|Inventors||Vijay Gangadhar Phadke|
|Original Assignee||Astec International Limited|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (83), Classifications (15), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the priority of U.S. Provisional Application No. 60/493,537, filed on Aug. 8, 2003, entitled “A Circuit for Maintaining Hold-Up Time While Reducing Bulk Capacitor Size and Improving Efficiency in a Power Supply”.
The present invention relates in general to power converter circuits and more particularly to a circuit that utilizes a boost converter front end to provide power factor correction.
A conventional AC to DC power converter typically includes a boost converter front end for power factor correction of the input bulk voltage generated from the AC input power source and a downstream DC to DC converter to convert the unregulated bulk voltage into an output voltage that satisfies the voltage regulation and transient response requirements of the power converter. In most applications, there is a “Power Hold-up” requirement for such converters. In other words, the DC output voltage generated by the downstream DC to DC converter is expected to stay in regulation for a predefined amount of time after the input power source has failed. When the input power source fails, a bulk capacitor in the power converter typically provides the necessary temporary power for the downstream DC to DC converter as it discharges. In most AC to DC converters, the minimum hold-up time is required to be the time necessary to maintain voltage regulation for at least one missing AC cycle of the input AC power source. Thus, this hold-up time is typically at least 16 mS for a 60 Hz line frequency AC power source and 20 mS for a 50 Hz line frequency AC power source.
Some power supply topologies, such as a flyback power converter, can operate up to a very wide duty cycle, with certain penalties on performance. Other topologies, such as the forward converter, cannot operate over a very wide duty cycle since, for very wide duty cycle variations, the efficiency drops significantly due to high peak currents. This significant drop in efficiency limits the practical input voltage tolerance of the DC to DC converter. As a result, for forward converters and other topologies that cannot operate over a very wide duty cycle, only a limited amount of energy stored in the bulk capacitor C1 is utilized during a power failure mode. For example, most DC to DC converters operate in the range of 100% of the normal bulk voltage level down to 75% if this level. Thus, for higher power, it is necessary to increase the size of the bulk capacitor to meet the hold-up requirement. This results in inefficient use of the available space in the power supply, affecting the power density.
As an example, a typical power factor corrected, 3 KW power supply receiving input power from a standard AC outlet and configured as in
In modern AC to DC and DC to DC power supplies, the requirement of higher power density is increasing day by day. Higher power converter switching frequencies reduce the sizes of the magnetic components significantly. Improvement in efficiency is also obtained by using better and faster semiconductor devices and more efficient topologies, which enables the size of the associated heat sinks to be reduced. However, the size of the bulk capacitor still remains the same, and this severely restricts advancements in higher power density. A circuit is therefore needed that will enable use of most of the energy stored in the bulk capacitance, to thereby reduce bulk capacitor requirements while also improving the efficiency of the converter.
A drawback of power converter 20 in
For example, a typical power factor corrected, 3 KW power supply receiving input power from a standard AC outlet and using the topology shown in
Another drawback of power converter 30 is that it requires an extra storage capacitor C2 which must be large enough to store enough energy to provide the required additional hold-up time. Still another drawback of power converter 30 is that it does not reduce the operational range of the DC to DC converter less than for other prior art converters. As a result, power converter 30 does not provide any performance gain over prior art converters.
For example, a typical power factor corrected, 3 KW power supply receiving input power from a standard AC outlet and configured as shown in
The charging of capacitor C1 in power converter 40 to a predetermined voltage is controlled by the circuit comprising the auxiliary winding, and a resistor R1 connected in series with a second switch SW2 and a diode D1 between one end of the auxiliary winding and one terminal of capacitor C1. The other terminal of capacitor C1 is connected to the second end of the auxiliary winding.
In operation, when switch SW1 of converter 40 closes, current flows in the primary of the transformer T1 and energy is stored therein. When the switch SW1 is opened, during the flyback period of converter 40, the polarity on the transformer T1 windings changes and the secondary rectifier diode D3 becomes forward biased. Diode D3 delivers power to a load as connected at the output terminals and stores energy in output capacitor C2. During this flyback period when switch SW1 is open, switch SW2 is turned on and capacitor C1 is charged to a predetermined voltage determined by the turns ratio between the primary winding and the auxiliary winding.
Thus, switch SW2 turns on only during the flyback period of converter 40. The voltage on capacitor C1 is usually selected low (around 50V or so). In normal operation, when the instantaneous voltage of the rectified AC pulse is higher than the voltage at which capacitor C1 is charged, diode D2 is reverse biased. Capacitor C1 will continue to hold its charge during this time. When this instantaneous voltage falls below the capacitor C1 voltage near the “valley point” of the rectified AC pulse, diode D2 becomes forward biased. As a result, capacitor C1 provides energy to transformer T1 to continue operation during this time. Capacitor C1 thus provides hold-up time during this period. Switch SW2 can also be held off when the charge on capacitor C1 is being used by converter 40 in order to reduce the peak currents in the transformer T1.
One drawback of the circuit in
The circuit in
A circuit is therefore needed that will enable use of most of the energy stored in the bulk capacitor to thereby reduce bulk capacitor size requirements, while also improving efficiency.
The present invention discloses a three-stage power converter that comprises a first boost converter stage having a bulk capacitor, a second boost converter stage, and a third DC to DC converter stage. The second boost converter stage is provided between the other two stages. The second boost converter stage provides a boosted voltage across a second capacitor when the voltage across the bulk capacitor is below a predetermined voltage level, thereby causing the voltage on the second boost converter output to be regulated at the predetermined voltage level. The second boost converter stage is turned off most of the time during normal operation through a diode in the second boost converter stage for extending the hold-up time while reducing the size of the capacitor in the second boost converter stage. This is accomplished by setting the voltage regulation point of the second boost converter stage to a valley point of a low frequency ripple on a bulk voltage delivered by the bulk capacitor in the first booster stage given that the second stage would detect an over-voltage on the output. When the bulk voltage in the bulk capacitor falls lower in the valley, due to low frequency ripple, the second boost stage will become active and will maintain the voltage level flat in the valley due to the fast control loop in the second boost converter stage. In operation, when the bulk voltage starts to fall during the hold-up time, the second boost converter or an intermediate converter boosts the falling voltage to maintain the DC input to the DC to DC converter between a narrow operating range and increases the operating duty cycle, so as to increase efficiency, reduce peak current and voltage stresses, reduce the size of output filter components and reduce the size of the bulk capacitance by up to half.
The present invention solves the problem of bulk capacitor size and power efficiency in a power converter by providing a circuit that more efficiently enables a significantly larger amount of the energy stored in the bulk capacitor to be used whenever there has been an input power failure. As a result, a much smaller bulk capacitor can be used to obtain the same hold-up time for the voltage output by the converter, while achieving increased efficiency. Alternatively, a much larger hold-up time can be attained for the same sized bulk capacitor.
An advantage of the inventive circuit is that it enables the converter to switch at a very high duty cycle, and thereby keep on delivering power to the converter's output terminals until the bulk capacitor has discharged to a very low level.
Another advantage of the present invention is that it improves the efficiency of the DC to DC converter by reducing its input voltage operating range.
Another advantage of the present invention is that it reduces the peak current and voltage stresses on the DC to DC converter components.
Another advantage of the present invention is that it reduces the size of the output filter components because of a higher steady state duty cycle.
The foregoing aspects and the attendant advantages of the present invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
A preferred embodiment of a circuit according to the present invention is shown at 100 in
Power converter 100 includes a diode 117 and diode 127. Diode 117 is connected in parallel with the series combination of inductor 112 and diode 116 of the first stage boost converter 110. Diode 117 functions only during an inrush current condition that occurs when the power supply turns on, in order to avoid saturating inductor 112 at startup. Diode 127 is a bypass diode connected in parallel with the series combination of inductor 122 and diode 126 of the second stage converter 120. It functions to bypass the second stage converter 120 when the converter 120 is not operating.
In operation, after the input AC voltage fails, the bulk capacitor 118 starts to discharge and the voltage across it starts to fall. The control signal input to switch 114 is typically a conventional PWM or PFC type drive signal (details not shown). Preferably, the first stage boost converter 110 is PFC controlled. The output DC voltage across capacitor 118 typically exhibits a low frequency ripple due to the slow control loop of the first stage boost converter 110, which is designed to sense voltage and current variation of an AC input line frequency of typically 50 Hz or 60 Hz and ignore the twice line frequency ripple. According to the present invention, a much smaller bulk capacitor can be used to obtain the same hold-up time for the voltage output by the converter. As a result, the bulk voltage on 118 has a considerable amount of low frequency ripple at higher loads.
As shown in
When the bulk voltage falls lower in the valley, due to low frequency ripple, the second stage boost converter 120 will become active and will maintain the voltage level flat in the valley due to its fast control loop. The resultant voltage across capacitor 128, which provides power to the downstream DC to DC converter stage 130, is shown in
If the first stage boost converter 110 is subjected to step loads or line transients at the input, the voltage on the bulk capacitor 118 can see an overvoltage. During such short instances, the duty cycle of the DC to DC converter 130 can shrink and then recover. For normal operation, however, the input voltage span is quite narrow, thus, the DC to DC converter 130 can operate at close to its maximum duty cycle, thereby reducing peak current and voltage stresses. As a result, the present invention enables the size of the components of the conventional output rectifier filter rail (details not shown) to be reduced.
Thus, the circuit shown in
For example, an exemplary power factor corrected, 3KW power supply, receiving input power from a standard AC outlet, as shown in
As described, modern AC to DC and DC to DC power supplies require ever increasing power density, thereby requiring increasingly higher switching frequencies in order to reduce the size of the components. Since the second stage boost converter 120, shown in
For the preferred embodiment of the inventive circuit shown in
The mode of operation for the present invention that works best depends on the requirements of a particular application. Typical requirements are minimizing power loss, minimizing bulk capacitor size, or maximizing the hold-up time, or a combination thereof.
The second stage boost converter shown in the embodiment in
As described, the present invention provides the required hold-up time while reducing the bulk capacitance and improving the efficiency of the DC to DC conversion.
For applications wherein a practical limitation such as ripple current rating, etc., does not allow the reduction of bulk capacitor size, the present invention provides the advantage of reducing the size of the output filter components, transformers, rectifiers, etc.
The present invention could be used in any power supply which uses a first stage boost converter. For the present invention, the second stage converter 120 is not limited to a boost converter topology. For example, in place of the second stage boost converter 120, a buck-boost converter could be used in such a way that it normally bucks down the output voltage of the first stage boost converter to a lower value. Thus, this alternative second stage provides a regulated, narrow band DC voltage to the downstream DC to DC converter 130. When the bulk voltage starts to fall during the hold-up time, this alternative circuit can switch and become a boost converter to boost the falling voltage and maintain the regulated DC input to the DC to DC converter 130.
Having disclosed exemplary embodiments, modifications and variations may be made to the disclosed embodiments while remaining within the scope of the invention as described by the following claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US6504497||May 16, 2001||Jan 7, 2003||Delta Electronics, Inc.||Hold-up-time extension circuits|
|US6512352 *||Jun 7, 2001||Jan 28, 2003||Koninklijke Philips Electronics N.V.||Active clamp step-down converter with power switch voltage clamping function|
|US6734655 *||Jun 30, 2000||May 11, 2004||Intel Corporation||Regulator design for inductive booster pump using pulse width modulation technique|
|US6798177 *||Oct 15, 2002||Sep 28, 2004||Arques Technology, Inc.||Boost-buck cascade converter for pulsating loads|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7330366 *||Jun 7, 2005||Feb 12, 2008||Delta Electronics, Inc.||DC-AC converter|
|US7408795 *||Apr 19, 2005||Aug 5, 2008||Vlt, Inc.||Energy storage and hold-up method and apparatus for high density power conversion|
|US7548441||Jun 1, 2005||Jun 16, 2009||Vlt, Inc.||Universal AC adapter|
|US7616465||May 28, 2008||Nov 10, 2009||Vlt, Inc.||Energy storage and hold-up method and apparatus for high density power conversion|
|US7729143 *||Apr 14, 2008||Jun 1, 2010||Acbel Polytech Inc.||Power supply having an extending hold-up time controlling unit|
|US7760524||Oct 17, 2007||Jul 20, 2010||Power Integrations, Inc.||Method and apparatus to reduce the volume required for bulk capacitance in a power supply|
|US7898238 *||Jul 1, 2008||Mar 1, 2011||Huettinger Elektronik Gmbh + Co. Kg||Generating an output DC voltage with a boost converter having a controlled pulse-duty factor|
|US7940540||May 27, 2009||May 10, 2011||Vlt, Inc.||Universal AC adaptor|
|US8125804 *||Jul 20, 2007||Feb 28, 2012||Shuguang He||Circuit for minimizing standby power in power supply systems|
|US8358098 *||Aug 9, 2010||Jan 22, 2013||Emerson Climate Technologies, Inc.||System and method for power factor correction|
|US8462527||May 6, 2011||Jun 11, 2013||Vlt, Inc.||Universal AC adaptor|
|US8476873||Aug 9, 2010||Jul 2, 2013||Emerson Climate Technologies, Inc.||System and method for current balancing|
|US8482935 *||Aug 16, 2011||Jul 9, 2013||Abb Oy||Transformer-isolated switching converter|
|US8493014||Aug 9, 2010||Jul 23, 2013||Emerson Climate Technologies, Inc.||Controller and method for estimating, managing, and diagnosing motor parameters|
|US8493039 *||Apr 14, 2011||Jul 23, 2013||Shenzhen China Star Optoelectronics Co. Ltd.||Cascade-connected boost circuit|
|US8508166||Aug 9, 2010||Aug 13, 2013||Emerson Climate Technologies, Inc.||Power factor correction with variable bus voltage|
|US8547051||Aug 15, 2012||Oct 1, 2013||Emerson Climate Technologies, Inc.||Controller and method for transitioning between control angles|
|US8558517 *||Sep 15, 2011||Oct 15, 2013||Compuware Technology Inc.||Power supply with virtual by-pass system|
|US8698433||Aug 9, 2010||Apr 15, 2014||Emerson Climate Technologies, Inc.||Controller and method for minimizing phase advance current|
|US8710820||Mar 31, 2010||Apr 29, 2014||Crane Electronics, Inc.||Switched capacitor hold-up scheme for constant boost output voltage|
|US8736238 *||Oct 19, 2010||May 27, 2014||Delta Electronics, Inc.||Buck and buck/boost converter systems having auxiliary circuits and method thereof|
|US8749165||Sep 25, 2011||Jun 10, 2014||Industrial Technology Research Institute||Light source driving device including a switching current adjustment circuit|
|US8773034 *||Aug 25, 2010||Jul 8, 2014||Koninklijke Philips N.V.||Power supply system for electronic loads|
|US8824167||Jul 18, 2011||Sep 2, 2014||Crane Electronics, Inc.||Self synchronizing power converter apparatus and method suitable for auxiliary bias for dynamic load applications|
|US8829868||Jul 18, 2011||Sep 9, 2014||Crane Electronics, Inc.||Power converter apparatus and method with output current sensing and compensation for current limit/current share operation|
|US8866551||Sep 10, 2012||Oct 21, 2014||Crane Electronics, Inc.||Impedance compensation for operational amplifiers used in variable environments|
|US8885308||Jul 18, 2011||Nov 11, 2014||Crane Electronics, Inc.||Input control apparatus and method with inrush current, under and over voltage handling|
|US8890630||Jul 18, 2011||Nov 18, 2014||Crane Electronics, Inc.||Oscillator apparatus and method with wide adjustable frequency range|
|US8964438||Nov 11, 2010||Feb 24, 2015||Eaton Industries Company||Power converter with hold up|
|US8981749||Oct 12, 2011||Mar 17, 2015||Blackberry Limited||Power converter system for mobile devices|
|US9024609||Dec 5, 2012||May 5, 2015||Pai Capital Llc||Circuit and method for providing hold-up time in a DC-DC converter|
|US9036376 *||Nov 12, 2012||May 19, 2015||Cognipower, Llc||Switched-mode compound power converter with main and supplemental regulators|
|US9041378||Jul 17, 2014||May 26, 2015||Crane Electronics, Inc.||Dynamic maneuvering configuration for multiple control modes in a unified servo system|
|US9088232||Aug 12, 2013||Jul 21, 2015||Emerson Climate Technologies, Inc.||Power factor correction with variable bus voltage|
|US9154061||Sep 30, 2013||Oct 6, 2015||Emerson Climate Technologies, Inc.||Controller and method for transitioning between control angles|
|US9160228||Feb 26, 2015||Oct 13, 2015||Crane Electronics, Inc.||Integrated tri-state electromagnetic interference filter and line conditioning module|
|US9203297 *||Dec 4, 2013||Dec 1, 2015||Hep Tech Co., Ltd.||AC/DC converter and method of correcting power factor|
|US9230726||Feb 20, 2015||Jan 5, 2016||Crane Electronics, Inc.||Transformer-based power converters with 3D printed microchannel heat sink|
|US9231479 *||Sep 5, 2013||Jan 5, 2016||Fuji Electric Co., Ltd.||Power supply device|
|US9240749||Aug 9, 2013||Jan 19, 2016||Emerson Climate Technologies, Inc.||Motor drive control using pulse-width modulation pulse skipping|
|US9293999||Sep 9, 2015||Mar 22, 2016||Crane Electronics, Inc.||Automatic enhanced self-driven synchronous rectification for power converters|
|US9413259||Jun 3, 2013||Aug 9, 2016||Vlt, Inc.||Universal AC adaptor|
|US9419538||Feb 24, 2012||Aug 16, 2016||Crane Electronics, Inc.||AC/DC power conversion system and method of manufacture of same|
|US9455643||May 14, 2015||Sep 27, 2016||Cognipower, Llc||AC input power converter with multi-functional inductor|
|US9564846||Jul 20, 2015||Feb 7, 2017||Emerson Climate Technologies, Inc.||Power factor correction with variable bus voltage|
|US9634593||Apr 26, 2013||Apr 25, 2017||Emerson Climate Technologies, Inc.||System and method for permanent magnet motor control|
|US9690349||Jul 30, 2015||Jun 27, 2017||Dell Products L.P.||Systems and methods for enhancing system hold up time using reverse charging of power supply unit|
|US9705433||Oct 5, 2015||Jul 11, 2017||Emerson Climate Technologies, Inc.||Controller and method for transitioning between control angles|
|US9735566||Dec 12, 2016||Aug 15, 2017||Crane Electronics, Inc.||Proactively operational over-voltage protection circuit|
|US9742183||Dec 9, 2016||Aug 22, 2017||Crane Electronics, Inc.||Proactively operational over-voltage protection circuit|
|US9774263||Aug 5, 2016||Sep 26, 2017||Schneider Electric It Corporation||Power converter with extended hold-up time|
|US9780635||Jun 10, 2016||Oct 3, 2017||Crane Electronics, Inc.||Dynamic sharing average current mode control for active-reset and self-driven synchronous rectification for power converters|
|US20050254272 *||Apr 19, 2005||Nov 17, 2005||Patrizio Vinciarelli||Energy storage and hold-up method and apparatus for high density power conversion|
|US20050270812 *||Jun 1, 2005||Dec 8, 2005||Patrizio Vinciarelli||Universal AC adapter|
|US20060039172 *||Aug 23, 2005||Feb 23, 2006||International Rectifier Corporation||Circuit to improve capacitor hold-up time in a converter circuit|
|US20060098461 *||Jun 7, 2005||May 11, 2006||Chih-Chang Lee||DC-AC converter|
|US20080284344 *||Jul 1, 2008||Nov 20, 2008||Huettinger Elektronik Gmbh + Co. Kg||Power supply unit for gas discharge processes|
|US20090097286 *||Apr 14, 2008||Apr 16, 2009||Acbel Polytech Inc.||Power supply having an extending hold-up time controlling unit|
|US20090185402 *||Jul 20, 2007||Jul 23, 2009||Chun Wah Lam||standby circuit with super low power consumption|
|US20100231164 *||Jun 9, 2009||Sep 16, 2010||Ls Industrial Systems Co., Ltd.||Charging system for electric vehicle|
|US20110031911 *||Aug 9, 2010||Feb 10, 2011||Emerson Climate Technologies, Inc.||Power factor correction with variable bus voltage|
|US20110031919 *||Aug 9, 2010||Feb 10, 2011||Emerson Climate Technologies, Inc.||Controller and method for minimizing phase advance current|
|US20110031920 *||Aug 9, 2010||Feb 10, 2011||Emerson Climate Technologies, Inc.||Controller and method for estimating, managing, and diagnosing motor parameters|
|US20110031941 *||Aug 9, 2010||Feb 10, 2011||Emerson Climate Technologies, Inc.||System and method for current balancing|
|US20110032738 *||Aug 9, 2010||Feb 10, 2011||Emerson Climate Technologies, Inc.||System and method for power factor correction|
|US20110122662 *||Oct 19, 2010||May 26, 2011||Fei Li||Buck and buck/boost converter systems having auxiliary circuits and method thereof|
|US20110216560 *||Mar 4, 2010||Sep 8, 2011||Sheng Ye||Two stage isolated switch-mode ac/dc converter|
|US20120044717 *||Aug 16, 2011||Feb 23, 2012||Abb Oy||Transformer-isolated switching converter|
|US20120146549 *||Aug 25, 2010||Jun 14, 2012||Koninklijke Philips Electronics N.V.||Power Supply System for Electronic Loads|
|US20130070497 *||Sep 15, 2011||Mar 21, 2013||Marcos Agoo Liquicia||Power supply with virtual by-pass system|
|US20130250621 *||May 20, 2013||Sep 26, 2013||Techtium Ltd.||High efficiency ac/dc power supply|
|US20140104889 *||Sep 5, 2013||Apr 17, 2014||Fuji Electric Co., Ltd.||Power supply device|
|US20140153306 *||Dec 4, 2013||Jun 5, 2014||Hep Tech Co., Ltd.||Ac/dc converter and method of correcting power factor|
|US20140232366 *||Nov 12, 2012||Aug 21, 2014||Cognipower, Llc||Switched-Mode Compound Power Converter With Main and Supplemental Regulators|
|US20160261144 *||Nov 11, 2013||Sep 8, 2016||Lg Innotek Co., Ltd.||Power supplying apparatus and wireless power transmitter|
|US20160268918 *||Nov 2, 2015||Sep 15, 2016||Lite-On Electronics (Guangzhou) Limited||Power supply with by-pass function and operation method|
|USRE44136||Oct 12, 2011||Apr 9, 2013||Vlt, Inc.||Energy storage and hold-up method and apparatus for high density power conversion|
|WO2011123680A2 *||Mar 31, 2011||Oct 6, 2011||Interpoint Corporation||Switched capacitor hold-up scheme for constant boost output voltage|
|WO2011123680A3 *||Mar 31, 2011||Dec 8, 2011||Interpoint Corporation||Switched capacitor hold-up scheme for constant boost output voltage|
|WO2015152920A1 *||Apr 3, 2014||Oct 8, 2015||Schneider Electric It Corporation||Isolated and efficient rectifier system|
|WO2017007772A1 *||Jul 5, 2016||Jan 12, 2017||Ionel Jitaru||Method and apparatus for reducing the size of the input bulk capacitor in ac to dc converters|
|WO2017019360A1 *||Jul 18, 2016||Feb 2, 2017||Dell Products L.P.||Systems and methods for enhancing system hold up time using reverse charging of power supply unit|
|WO2017019361A1 *||Jul 18, 2016||Feb 2, 2017||Dell Products L.P.||Systems and methods for programmable system ride-through and hold-up|
|U.S. Classification||323/222, 323/224, 323/284|
|International Classification||H02M3/28, H02M1/42, G05F1/652, H02M1/00, G05F1/656|
|Cooperative Classification||H02M3/28, H02M2001/0096, H02M1/4225, Y02B70/126, H02M2001/007|
|European Classification||H02M1/42B5, H02M3/28|
|Aug 6, 2004||AS||Assignment|
Owner name: ASTEC INTERNATIONAL LIMITED, HONG KONG
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:PHADKE, VIJAY GANGADHAR;REEL/FRAME:015674/0933
Effective date: 20040802
|Dec 14, 2009||FPAY||Fee payment|
Year of fee payment: 4
|Jan 24, 2014||REMI||Maintenance fee reminder mailed|
|Jun 13, 2014||LAPS||Lapse for failure to pay maintenance fees|
|Aug 5, 2014||FP||Expired due to failure to pay maintenance fee|
Effective date: 20140613